NEAR Orbit Around Asteroid 433 Eros

Images of Eros

Craterscape

The inside of Eros' largest crater, which dominates one side of the asteroid, was
captured in this NEAR Shoemaker image taken May 19, 2000, from an orbital altitude
of 50 kilometers (31 miles). The section shown is about one quarter of the whole
crater and is approximately 1.4 kilometers (0.8 miles) across. A cluster of large
boulders sits at the bottom of the pit, and features as small as 4 meters (13 feet)
across can be distinguished. More boulders dot the walls, which are also mottled by
variations in the reflectivity of the surface layer of rock and soil, known as "regolith."
(Image 0134136322)

Pretty Sharp

Pictures taken during the low-orbit phase of NEAR Shoemaker's mission to Eros
are revealing the true appearance of an asteroid's surface. Eros is turning out to
have diverse surface types ranging from flat to hilly, smooth to rocky, and
monotonously cratered to unique in character.

This picture was taken for "optical navigation," that is, plotting the spacecraft's
course by tracking the positions of the landmarks below. It caught a spectacular
view of a horizon sculpted by worn, degraded craters and punctuated by jagged
boulders. The angular boulder at the center of the frame is about 60 meters (197
feet) tall, or two-thirds the length of a football field. Angular rocks are very common
in nature; the corners form as a rock is chipped out of a larger mass.

This image was taken May 18, 2000, from an orbital altitude of 50 kilometers (31
miles). The whole scene is about 1.4 kilometers (0.8 miles) across, and it shows
features as small as 4 meters (13 feet).
(Image 0134030614)

Over the Edge

Some of the most aesthetically pleasing views of Eros from NEAR Shoemaker have
been obtained when the camera looks at the asteroid's horizon. This image was taken
on May 15, 2000, from an orbital altitude of 52 kilometers (32 miles). The whole scene
is about 1.4 kilometers (0.8 miles) across, and it shows features as small as 4 meters
(13 feet) across. With the Sun high overhead, shadows are minimized and surface
brightness variations stand out. Mottled brightness patterns as small as 30 meters (98
feet) across are evident near the horizon.
(Image 0133835914)

Chock Full o' Rocks

Low-orbit images of Eros taken by NEAR Shoemaker have shown an amazing
abundance of boulders of all sizes strewn across the asteroid's surface. This image
was taken on May 14, 2000, from an orbital altitude of 50 kilometers (31 miles). The
scene is about 1.8 kilometers (1.1 miles) across and includes features as small as
4 meters (13 feet). The field of boulders at the upper right is one of the rockiest parts
of Eros discovered so far. The largest of the boulders is about 60 meters (197 feet)
in diameter, nearly two-thirds the length of a football field.
(Image 0133699128)

Looking Down

NEAR Shoemaker photographs Eros under a variety of lighting and viewing geometries
suited to different science objectives. Taken with the Sun high in the sky, images with
few shadows are best for mapping the color properties of the surface. Conversely,
images taken from directly above a surface with oblique illumination are best for
seeing landforms, because shadowing highlights the subtle shape changes on the
asteroid's surface.

This image was taken at the latter geometry on May 11, 2000, from an orbital altitude of
52 kilometers (33 miles). The whole scene is about 1.8 kilometers (1.1 miles) across,
and shows features as small as 4 meters (13 feet). The rounded nature of the
landforms results from formation of small impact craters over the eons. Sharp
topography is eroded away by this process, and the surface is blanketed and
smoothed by the fragmental debris, or "regolith." The large boulders scattered
throughout the scene are the largest fragments of the rocky regolith.
(Image 0133428128)

Putting Eros into Perspective

Though NEAR Shoemaker returns images that reveal a wealth of detail about the landforms on Eros' surface,
appreciating the scale of these features can be a little difficult without roads, buildings, trees or other familiar
landmarks.

This image, taken May 4, 2000, from an orbital altitude of 50 kilometers (31 miles), shows a variety of small
surface features. The whole scene is about 1.8 kilometers (1.1 miles) across. To better visualize the size of
the features, a to-scale Empire State Building is inset at the bottom of the image. The shallow, linear troughs
in the lower part of the photo (marked by arrows) are 60 meters (197 feet) across. The boulder on the floor of
the large crater at right is 30 meters (98 feet) across, whereas the crater itself measures about 800 meters
(2,625 feet) across.
(Image 0132926922)

Horizon View

This image of Eros, taken from the NEAR Shoemaker spacecraft on May 2, 2000, from an orbital altitude of
52 kilometers (32 miles), shows a view toward Eros' horizon. The section shown is about 1.8 kilometers
(1.1 miles) across. This particular view provides a snapshot of three of the most common types of features
seen on the asteroid: craters whose rims have been rounded by erosion due to smaller impacts and
blanketing by the impact debris, or regolith (impact debris); variations in the brightness of material on the
walls of the craters; and a scattering of boulders ranging in size from nearly 100 meters (328 feet) down to
about 8 meters (26 feet).
(Image 0132668988)

The View from Low Orbit

This image of Eros, taken from the NEAR Shoemaker spacecraft on May 1, 2000, is among the first to be
returned from "low orbit." Between May and August, the spacecraft will orbit at altitudes near 50 kilometers (31
miles) or less. This will be the prime period of activity for some of the spacecraft's science instruments. The
X-ray / gamma-ray spectrometer will build up maps of chemical abundances, while the laser rangefinder
measures the shape of Eros to within meters (a few feet). At the same time the magnetometer will watch for
indications of Eros' magnetic field and the near-infrared spectrometer will map rock types.

The imager will take pictures of the entire surface of Eros that capture features as small as 4 meters (13 feet)
across. This particular image, taken from an orbital altitude of 53 kilometers (33 miles), shows a scene about
1.8 kilometers (1.1 miles) across. Numerous craters and boulders as small as 8 meters (26 feet) across dot
the landscape. The large, rectangular boulder at the upper right is 45 meters (148 feet) across.
(Image 0132577092)

Settling Down for a Long Map

From April through August 2000, the NEAR Shoemaker spacecraft will map Eros in
very high spatial resolution from a low altitude. Images, covering the whole asteroid,
will show features as small as 4 meters (13 feet) across. This image, which
provides a taste of the exquisite detail to come, was taken April 30, 2000, from an
orbital height of 76 kilometers (47 miles). Hours later, an engine firing placed the
spacecraft into a 50-kilometer (31-mile) altitude orbit. The image shows features as
small as 6 meters (19 feet) across. The whole scene is 3 kilometers (1.8 miles)
across.
(Image 0132482558)

Down, Down, Down

As the NEAR Shoemaker spacecraft continues its descent to lower orbits around
Eros, smaller and smaller surface details are becoming visible. This image was
taken April 29, 2000, from an orbital height of 84 kilometers (52 miles), just before
the engine firing that placed NEAR in a 50-kilometer (31-mile) altitude orbit. The
image shows features as small as 7 meters (23 feet) across and boulders a mere
tens of meters in size. The whole scene is 3.2 kilometers (2 miles) across.
(Image 0132376638)

Nibbled at the Edges

The longtime battering of Eros' surface has produced an amazing variety of
landforms in which craters overlap each other. This NEAR Shoemaker image, taken
April 5, 2000, from an orbital height of 106 kilometers (66 miles), shows some of the
features that can result from intense surface cratering. Just to the left of center,
several craters have been superimposed on one another to form an interesting,
lobed depression. Two craters in the upper right of the image overlap to produce a
scalloped-edged depression 1.7 kilometers (1.06 miles) across.
(Image 0130350940)

A Smorgasbord of Landforms

The images of Eros being returned by NEAR Shoemaker reveal a surprising diversity of interesting features. Many people's preconceptions of asteroids come
from cinematic special effects that depict asteroids as little more than oversized tumbling rocks, perhaps tattered by strange, jagged landforms.

This image, taken April 17, 2000, from a distance of 101 kilometers (63 miles), suggests three words that could describe this asteroid: rocky, ridged, and
rounded. The large boulder in the far left-center of the image measures more than 70 meters (230 feet) across. The ridge in the lower section of the frame is
part of a feature that continues around a substantial part of the asteroid's middle. And although some of the small craters appear fresh and sharp, most of
their rims have been rounded off by eons of relentless pounding by small, impacting meteors.
(Image 0131276455)

Eros Up Close

Since April 11, the NEAR Shoemaker spacecraft has orbited Eros at an altitude of 100 kilometers (62 miles) from
the asteroid's center. Images acquired from this orbit will be used to make a high-resolution map of the illuminated
portion of the asteroid. Each spot on the surface will be imaged under a variety of lighting and viewing conditions to
bring out different features.

In this image, taken April 17, 2000, from a height of 101 kilometers (63 miles), the shadows highlight small-scale
surface features. The surface is pockmarked with craters ranging in size up to the 2.8-kilometer (1.74-mile)
diameter crater in the center of the image. The smallest craters which can be resolved are about 20 meters (65 feet)
across. In lower right corner of the image, 20-meter boulders can be seen that were not evident in images from
higher altitudes.
(Image 0131288775)

Impact at High Noon

For people who live in mountain valleys, daylight can be a short-lived
experience. Mountains to the east make the Sun rise later in the morning,
while mountains to the west make the Sun set earlier in the evening. The
brevity of daytime in a valley is accentuated during the shortened days of
winter.

The floor of the 5.5-kilometer (3.4-mile) diameter impact crater that dominates
one face of Eros experiences the ultimate in short daylight hours. Three
factors conspire to make this true. Firstly, Eros rotates rapidly, once every 5.27
hours. Secondly, the crater's 0.9-kilometer (0.56-mile) high walls tend to block
direct sunlight from the floor, even while the outside of the crater is
illuminated. Thirdly, during the current season on Eros, the Sun never makes
it high in the sky in this location.

This NEAR Shoemaker image, taken April 1, 2000, from a range of 209
kilometers (130 miles), caught the crater near local noon with the Sun highest
in the sky. On that day, a hardy astronaut standing at the bottom of the crater
would have experienced 1 hour and 45 minutes of daylight.
(Image 0129999407)

The Record of What Came Before

Impact craters are the most common, pervasive, and scientifically informative landforms
on Eros. This image from NEAR Shoemaker, taken March 20, 2000, from a range of 206
kilometers (128 miles), shows a highly cratered region of the asteroid. The whole scene
is 7.4 kilometers (4.6 miles) across. Craters are formed by the explosive impacts of
asteroid fragments that have rained onto the surface over the eons. A freshly exposed
surface will have fewer craters than a surface exposed to space for a longer time. The
great number of impact craters in the pictured region indicates that it has been an
extremely long time since this region was wiped clean, or "resurfaced," by a geologic
process such as the chipping off of part of the asteroid. Also, the greater abundance of
smaller craters reveals that small asteroid fragments have impacted Eros more
frequently than large asteroid fragments.
(Image 0128933396)

Eros' North Pole

For much of the past five weeks, imaging activities on the NEAR Shoemaker spacecraft
have focused on the high northern latitudes of Eros. The point at which the Sun is directly
overhead - known as the "subsolar point" - has been steadily moving from Eros' northern
regions toward the equator as the asteroid's seasons progress. As this happens, the
northern hemisphere is illuminated less and less, and previously dark southern latitudes
progressively come into view.

In this image, taken March 19, 2000, from a range of 205 kilometers (127 miles), the
asteroid's north pole is in the upper right of the frame. The whole scene is 7.4 kilometers
(4.6 miles) across.
(Image 0128883708)

Eros in a Different Light

During the 28 days the NEAR Shoemaker spacecraft circled Eros in a
200-kilometer (124-mile) altitude orbit, it imaged parts of the surface under
a variety of lighting and viewing conditions. The different views of the
surface allow study of small-scale morphology, analysis of albedo and
color variations, and construction of topographic models from stereo
images.

This image, taken April 2, 2000, from a range of 199 kilometers (123
miles), shows the effects of lighting changes. At the bottom of the frame,
sunlight illuminates the surface at a grazing angle. The strong shadows
bring out subtle landforms like the gentle undulations in the surface, visible
at the lower center. At the top of the frame, sunlight strikes the surface at a
high angle and shadows become subdued, bringing out brightness
variations like those on the wall of the large, 5.5-kilometer (3.4-mile)
diameter crater at left.
(Image 0130112939)

The Importance of Lighting

The way in which Eros' craters are illuminated makes a big difference in their appearance in images from NEAR Shoemaker.
This image was taken March 8, 2000, from a range of 205 kilometers (127 miles). In the foreground, craters are obliquely
illuminated. The brightness differences between Sun-facing and shaded slopes bring out the morphologic details in the
asteroid's surface. In the background the Sun is nearly overhead, and the lack of shadows makes details appear subdued.
But these "high-Sun" conditions bring out inherent brightness differences in surface materials, such as the bright walls in the
four craters near the center of the image.
(Image 0127886509)

Boulders, Boulders, Boulders

One of the most striking features in NEAR Shoemaker images of Eros' surface is the abundance of very large boulders. This image of
the southwestern part of the saddle region, taken March 6, 2000, from a range of 201 kilometers (125 miles), shows a particularly
boulder-rich part of the surface. Many of the huge rocks are 50 meters (164 feet) or more in diameter. They are believed to be fragments
of Eros' native rock, shattered over the eons by formation of impact craters. The impacting projectiles themselves were pulverized by the
impact process and survive only as fine debris mixed into the regolith.
(Image 0127751446)

April Fool's Crater

Lighting and viewing geometries make a huge difference in the appearance
of Eros' surface features. One of the most striking examples is the
2.7-kilometer (1.68-mile) diameter crater shown in these two images. The
image at left, looking at the crater nearly edge-on, was taken February 16,
2000, from a range of 341 kilometers (212 miles). The image at right was
taken high over the crater on March 2, 2000, from a range of 226 kilometers
(140 miles). In the first image the only visible part of the crater's interior is
the far, bright wall, which at the time was well-lit. The lighting, in combination
with the particular viewing angle, make the crater appear stunningly bright.
In the second view, the brighter material occupies only part of the
slightly-shaded interior, greatly reducing the overall brightness contrast
between the crater and the surrounding terrain.
(Images 0126124237 and 0127390944)

Two Very Different Asteroids

The NEAR Shoemaker spacecraft has scored two important firsts in the exploration of asteroids: it's
the first to orbit an asteroid, Eros, and the first to encounter a denizen of the outer reaches of the
asteroid belt, the C-type asteroid Mathilde. In a scheme that reflects how they have historically been
a topic for astronomy, not geology, asteroids are classified into groups based on their colors as
observed through telescopes.

The two major classes of asteroids are called S-types and C-types. S-types, whose colors are
consistent with "stony" or rocky compositions, prevail among asteroids that orbit closer to the Sun
than the mid-point of the asteroid belt. Eros and the two asteroids encountered briefly by the Galileo
spacecraft on its way to Jupiter -- Gaspra and Ida -- are all S-types. C-types like Mathilde have a dark
gray color consistent with a "carbonaceous" composition, rich in carbon compounds and other dark
materials. They prevail in the outer part of the asteroid belt.

In this montage, Mathilde (at left) and Eros (at right) are shown at the same scale, as they were
imaged by NEAR Shoemaker from about 1,800 kilometers (1,116 miles) on June 27, 1997, and
February 12, 2000, respectively. Mathilde is 56 kilometers (35 miles) across, and Eros is 33
kilometers (21 miles) long and 13 kilometers (8 miles) wide. However, Mathilde's brightness is
greatly exaggerated for viewing purposes -- it's actually six times darker than Eros, with about the
same reflectivity as soot!
(Image 0128064932)

Eros Color at Higher Resolution

As the NEAR Shoemaker spacecraft descends into lower orbits around Eros, it continually returns higher spatial resolution images of the asteroid. The true color image at left was
taken February 12, 2000, from a range of 1,748 kilometers (1,083 miles), and shows details only as small as 180 meters (590 feet) across. It was taken two days before orbit insertion,
as part of an image sequence designed to provide moderate-resolution color mapping of Eros at a near-constant viewing geometry. The true color image inset at right was taken
February 29 from a range of 283 kilometers (175 miles) and shows much smaller details only 27 meters (89 feet) across. The higher spatial resolution (by a factor of six) brings out a
whole class of surface details that were either invisible or at the margin of visibility in the earlier images. For example, the bright material on the wall of the large crater in the inset
image is barely evident in the lower-resolution image at left, but by virtue of its limited spatial coverage the inset image lacks information on the crater's regional geologic setting.
NEAR Shoemaker's imaging strategy makes use of both types of images, with lower-resolution images providing "context" for higher-resolution images that bring specific features into
sharper focus.
(Product of images 0125748893, 0125748895, 0125748897, 0127229466, 0127229468, 0127229470)

Eros Surface Morphology

On March 10, 2000, this image of Eros was acquired by the imager on the NEAR Shoemaker spacecraft,
from a range of 206 kilometers (127 miles). The area shown in the image is 10 kilometers (6.2 miles) across,
and the smallest detail visible is 20 meters (65 feet) across. Here, the spacecraft was over the shaded interior
of the "saddle," looking over the north polar region to the limb. The shadowing at the upper right is due to
oblique lighting. The narrowness of the illuminated part of Eros in the center of the frame results from
viewing the narrow "waist" of Eros' irregular peanut-like shape.

This image is from one of a large number of imaging sequences acquired during the first of two
"200-kilometer" (124-mile) orbits. The second 200-kilometer orbit, in autumn 2000, will provide similar
views of southern latitudes. The purpose of many of the sequences in this orbit is to view the northern and
equatorial latitudes of the asteroid under conditions similar to those at the time of this image, looking straight
down on a part of the surface (called a "low emission angle") while the surface is obliquely illuminated (called
a "high incidence angle"). The resulting views bring out surface morphology and are crucial to making a global
map of Eros.
(Image 0128064932)

Eros' North Polar Region

On March 11, 2000, this image of Eros' north polar region was acquired by the imager on the NEAR
Shoemaker spacecraft, from a range of 206 kilometers (127 miles). The area shown in the image is 10
kilometers (6.2 miles) across. Most of the north polar region is heavily cratered but the region to the left
(part of the "saddle") has a lower crater density, indicating that the surface has been modified since it first
formed. Eros' rotational axis lies nearly parallel to its orbital plane, much as with the planet Uranus, giving
the asteroid exaggerated "seasons." Now, it is northern summer and the north pole is in continuous sunlight.
The Sun will set there this June, at Eros' equivalent of Earth's autumnal equinox. At that time, Eros' south
pole will begin 12 months of continuous illumination while the north pole remains in darkness. (Image
0128166012)

The Long View of Eros

This image looking down the length of Eros was taken from the NEAR Shoemaker spacecraft on March 10, 2000, from a range of 206 kilometers
(127 miles). At once, it shows many of the landforms revealed in the last month to be characteristic of this tiny world. The part of the surface
shown here is covered by craters of all sizes, right down to the limit of image resolution. Many of the largest craters, such as the two at upper
left, have conspicuous brightness ("albedo") markings on their interior walls. At the upper left is a portion of the ridge that nearly wraps around
Eros' waist. Near the center of the image, oriented from the upper right to lower left, are several broad troughs, or grooves, about 200 meters (656
feet) wide. The three boulders on the far horizon are about 80 meters (262 feet) across - each nearly the size of a football field.

The area shown in the image is 10 kilometers (6.2 miles) high. To put the asteroid's size into human perspective, a famous New York landmark is
shown inset at the lower left.
(Image 0128058662)

Eros, in stereo

Stereo imaging will be an important tool on NEAR for geologic analysis of Eros, because it provides three-dimensional information on the
asteroid's landforms and structures. This anaglyph can be viewed using red-blue glasses to show Eros in stereo. It was constructed from
images taken on February 14 and 15 that showed the same part of Eros from two slightly different viewing perspectives. The smallest
feature visible is 100 feet (30 meters) across. For this image the spacecraft position was not optimum for stereo, but it will improve over
the next few days allowing better 3-D views.